This invention relates to steel chain links, having application primarily, though not exclusively, in tire chains for heavy duty vehicles, such as for mining, quarrying, earth-moving and forestry applications, to protect the rubber tires on one or more axles of such vehicles and/or provide additional traction.
Tire chains of the type with which this invention is concerned have a treed portion spanning the tread of a tire and two flanking side-wall portions that respectively span a portion of the inner and outer side-walls of the tire. The chain is composed of links that extend substantially normal to the surface of the tire and connecting rings or connectors interconnecting the links to form a net of a desired pattern. This type of tire chain is referred to as xe2x80x9ca tire chain of the type set forthxe2x80x9d below.
Tread links each comprise a base portion to provide a smooth, suitably large contact area with a tire in use; a medial portion formed with at least one opening through which a connector can be threaded, with the lateral thickness being reduced relatively to the base portion to permit increased lateral movement with respect to the connectors; and a head portion of a shape suited to the intended application of the chain. A broad head portion that may have a diamond shape decreases the mesh opening and thereby increases protection, whilst a relatively thinner head portion decreases protection and increases traction. Protrusions in the form of ribs or buttons of the material of the link of various configurations, shapes and sizes may be provided to increase traction, but these have limited long term value as they wear away fairly rapidly in use, particularly if they are operated in highly abrasive conditions such as chrome mines, smelting works and on silica. Whilst increasing the hardness of the link to inhibit wear is possible, the benefits obtained are usually more than counteracted by the increased tendency of the link to fracture or break in use.
This invention seeks to provide a link for a tire chain that has a reduced tendency to slip in use and/or has increased resistance to wear. Optionally the invention seeks to provide a method of modifying a tire chain to increase the traction and/or wear resistance properties thereof; to provide a method of restoring tire chains that have worn in use; and/or to provide parts or components for use in the aforesaid methods or in a tire chain.
The invention provides a link for a tire chain of the type set forth comprising a base portion, a medial portion and a head portion, characterised in that the link has at least one traction member of a material that is relatively harder than the material of the link partially embedded in the head portion and partially exposed on the surface of the head portion.
The link may have the following features, alone or in combination:
the traction member may be in the form of a solid body, such as a cylinder that is preferably substantially round in cross-section or a thick plate locked in an opening formed in the head portion of the link;
a plurality of such solid body traction members may be arranged at desired positions on the head, either adjacent to or spaced apart from one another;
the traction member may be in the form of a particle in which event a plurality of such particles are preferably consolidated in a cemented compact or steel matrix;
the traction member is of a suitable hard, abrasion resistant carbide, nitride and the like compounds in particle, cemented or sintered form;
the traction member or members are secured to a body that is weldable to the head portion of the link. The latter form is particularly suited to restoring links that have worn in use, but may also be used for new chain links.
The invention also includes a tire chain of the type set forth characterised by having at least one link of the invention.
Further features, variants, and/or advantages, of the invention will become apparent from the following, non-limiting description made with reference to the accompanying schematic drawings of presently preferred examples of the invention and from the claims, which are to be regarded as an integral part of this description.